Method for terminal transmitting sidelink control information in wireless communication system and terminal using same

ABSTRACT

Provided are a method and a device for a terminal transmitting sidelink control information (SCI) in a wireless communication system. The method enables generating an SCI format and transmitting the generated SCI format to another terminal, wherein the SCI format is transmitted after determining the number of bits to be actually used in a resource allocation field included in the SCI format, and after zero-padding bits other than the number of bits to be actually used in the resource allocation field.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communication and, more particularly, to a method for a UE to transmit sidelink control information in a wireless communication system, and a UE using the same.

Related Art

In International Telecommunication Union Radio communication sector (ITU-R), a standardization task for International Mobile Telecommunication (IMT)-Advanced, that is, the next-generation mobile communication system since the third generation, is in progress. IMT-Advanced sets its goal to support Internet Protocol (IP)-based multimedia services at a data transfer rate of 1 Gbps in the stop and slow-speed moving state and of 100 Mbps in the fast-speed moving state.

Long-Term Evolution (LTE)-Advanced (LTE-A), which is a system standard to meet IMT-Advanced requirements and an enhancement of LTE based on an orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission mode, was submitted to ITU-R and was approved by the 3rd Generation Partnership Project (3GPP) as a fourth-generation mobile communication standard.

The 3GPP has been conducting studies on V2X as one study item (SI) for LTE Release 14. V2X refers to vehicle-to-everything communication and includes V2V, that is, vehicle-to-vehicle communication.

In performing V2V communication, a UE may need to transmit sidelink control information to another UE. In this case, it may be necessary to consider how to configure the sidelink control information, for example, which fields are included to configure the sidelink control information and whether to vary or fix the length of a resource allocation field as the number of resources allocated for V2V communication changes.

SUMMARY OF THE INVENTION

An aspect of the present invention is to provide a method for a UE to transmit sidelink control information in a wireless communication system, and a UE using the same.

In one aspect, provided is a method for transmitting, by a user equipment (UE), sidelink control information (SCI) in a wireless communication system. The method includes generating an SCI format and transmitting the generated SCI format to another UE. The SCI format is transmitted by determining a number of bits to be actually used in a resource allocation field of the SCI format and padding, with zeros, bits other than the bits to be actually used in the resource allocation field.

A total number of bits comprised in the SCI format may be a fixed value.

The total number of bits may be 48 bits.

A number of bits comprised in the resource allocation field of the SCI format may be a fixed value.

The number of bits comprised in the resource allocation field may be 8 bits.

The number of bits to be actually used in the resource allocation field of the SCI format may be determined depending on a number of subchannels allocated for the UE.

The subchannels may comprise a plurality of contiguous resource blocks.

In another aspect, provided is a device for transmitting sidelink control information (SCI) in a wireless communication system. The device includes a radio frequency (RF) unit to transmit and receive a radio signal and a processor connected to the RF unit to operate. The processor generates an SCI format and transmits the generated SCI format to another UE, and the SCI format is transmitted by determining a number of bits to be actually used in a resource allocation field of the SCI format and padding, with zeros, bits other than the bits to be actually used in the resource allocation field.

Unlike downlink control information that a base station (BS) transmits to a user equipment (UE), sidelink control information that a UE transmits to another UE in sidelink communication may have a fixed bit size and may be configured with a fixed-size resource allocation field regardless of the size of allocated resources. Accordingly, it is possible to reduce complexity and to easily detect sidelink control information. Further, when a resource allocation field in a sidelink control information format is configured with a fixed number of bits, in which the number of bits actually used in the resource allocation field is smaller than the fixed number of bits, the remaining bits may be padded with zeros and may be used as a virtual CRC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 is a diagram showing a wireless protocol architecture for a user plane.

FIG. 3 is a diagram showing a wireless protocol architecture for a control plane.

FIG. 4 shows a basic structure for ProSe.

FIG. 5 shows the deployment examples of types of UE performing ProSe direct communication and cell coverage.

FIG. 6 illustrates scenarios in which V2V communication is performed.

FIG. 7 illustrates a signaling process for V2V communication between UEs and a BS.

FIG. 8 illustrates a signaling process for V2V communication between UEs.

FIG. 9 illustrates a method for determining the payload size of DCI format 5A according to proposed method #1.

FIG. 10 illustrates a case where proposed method #2 is applied.

FIG. 11 illustrates a method in which proposed method #2 is applied.

FIG. 12 is a block diagram illustrating a device to implement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system.

The wireless communication system may be referred to as an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) or a Long Term Evolution (LTE)/LTE-A system, for example.

The E-UTRAN includes at least one base station (BS) 20 which provides a control plane and a user plane to a user equipment (UE) 10. The UE 10 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The BS 20 is generally a fixed station that communicates with the UE 10 and may be referred to as another terminology, such as an evolved node-B (eNB), a base transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20 are also connected by means of an S1 interface to an evolved packet core (EPC) 30, more specifically, to a mobility management entity (MME) through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway (P-GW). The MME has access information of the UE or capability information of the UE, and such information is generally used for mobility management of the UE. The S-GW is a gateway having an E-UTRAN as an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network can be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. Among them, a physical (PHY) layer belonging to the first layer provides an information transfer service by using a physical channel, and a radio resource control (RRC) layer belonging to the third layer serves to control a radio resource between the UE and the network. For this, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a user plane. FIG. 3 is a diagram showing a wireless protocol architecture for a control plane. The user plane is a protocol stack for user data transmission. The control plane is a protocol stack for control signal transmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with an information transfer service through a physical channel. The PHY layer is connected to a medium access control (MAC) layer which is an upper layer of the PHY layer through a transport channel. Data is transferred between the MAC layer and the PHY layer through the transport channel. The transport channel is classified according to how and with what characteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of a transmitter and a receiver, through a physical channel The physical channel may be modulated according to an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and use the time and frequency as radio resources.

The functions of the MAC layer include mapping between a logical channel and a transport channel and multiplexing and demultiplexing to a transport block that is provided through a physical channel on the transport channel of a MAC Service Data Unit (SDU) that belongs to a logical channel The MAC layer provides service to a Radio Link Control (RLC) layer through the logical channel

The functions of the RLC layer include the concatenation, segmentation, and reassembly of an RLC SDU. In order to guarantee various types of Quality of Service (QoS) required by a Radio Bearer (RB), the RLC layer provides three types of operation mode: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provides error correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer is related to the configuration, reconfiguration, and release of radio bearers, and is responsible for control of logical channels, transport channels, and PHY channels. An RB means a logical route that is provided by the first layer (PHY layer) and the second layers (MAC layer, the RLC layer, and the PDCP layer) in order to transfer data between UE and a network.

The function of a Packet Data Convergence Protocol (PDCP) layer on the user plane includes the transfer of user data and header compression and ciphering. The function of the PDCP layer on the user plane further includes the transfer and encryption/integrity protection of control plane data.

What an RB is configured means a process of defining the characteristics of a wireless protocol layer and channels in order to provide specific service and configuring each detailed parameter and operating method. An RB can be divided into two types of a Signaling RB (SRB) and a Data RB (DRB). The SRB is used as a passage through which an RRC message is transmitted on the control plane, and the DRB is used as a passage through which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRC layer of an E-UTRAN, the UE is in the RRC connected state. If not, the UE is in the RRC idle state.

A downlink transport channel through which data is transmitted from a network to UE includes a broadcast channel (BCH) through which system information is transmitted and a downlink shared channel (SCH) through which user traffic or control messages are transmitted. Traffic or a control message for downlink multicast or broadcast service may be transmitted through the downlink SCH, or may be transmitted through an additional downlink multicast channel (MCH). Meanwhile, an uplink transport channel through which data is transmitted from UE to a network includes a random access channel (RACH) through which an initial control message is transmitted and an uplink shared channel (SCH) through which user traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that are mapped to the transport channel include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

The physical channel includes several OFDM symbols in the time domain and several subcarriers in the frequency domain. One subframe includes a plurality of OFDM symbols in the time domain. An RB is a resources allocation unit, and includes a plurality of OFDM symbols and a plurality of subcarriers. Furthermore, each subframe may use specific subcarriers of specific OFDM symbols (e.g., the first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval (TTI) is a unit time for subframe transmission.

The RRC state means whether or not the RRC layer of UE is logically connected to the RRC layer of the E-UTRAN. A case where the RRC layer of UE is logically connected to the RRC layer of the E-UTRAN is referred to as an RRC connected state. A case where the RRC layer of UE is not logically connected to the RRC layer of the E-UTRAN is referred to as an RRC idle state. The E-UTRAN may check the existence of corresponding UE in the RRC connected state in each cell because the UE has RRC connection, so the UE may be effectively controlled. In contrast, the E-UTRAN is unable to check UE in the RRC idle state, and a Core Network (CN) manages UE in the RRC idle state in each tracking area, that is, the unit of an area greater than a cell. That is, the existence or non-existence of UE in the RRC idle state is checked only for each large area. Accordingly, the UE needs to shift to the RRC connected state in order to be provided with common mobile communication service, such as voice or data.

When a user first powers UE, the UE first searches for a proper cell and remains in the RRC idle state in the corresponding cell. The UE in the RRC idle state establishes RRC connection with an E-UTRAN through an RRC connection procedure when it is necessary to set up the RRC connection, and shifts to the RRC connected state. A case where UE in the RRC idle state needs to set up RRC connection includes several cases. For example, the cases may include a need to send uplink data for a reason, such as a call attempt by a user, and to send a response message as a response to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performs functions, such as session management and mobility management.

In the NAS layer, in order to manage the mobility of UE, two types of states: EPS Mobility Management-REGISTERED (EMM-REGISTERED) and EMM-DEREGISTERED are defined. The two states are applied to UE and the MME. UE is initially in the EMM-DEREGISTERED state. In order to access a network, the UE performs a process of registering it with the corresponding network through an initial attach procedure. If the attach procedure is successfully performed, the UE and the MME become the EMM-REGISTERED state.

In order to manage signaling connection between UE and the EPC, two types of states: an EPS Connection Management (ECM)-IDLE state and an ECM-CONNECTED state are defined. The two states are applied to UE and the MME. When the UE in the ECM-IDLE state establishes RRC connection with the E-UTRAN, the UE becomes the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes Si connection with the E-UTRAN. When the UE is in the ECM-IDLE state, the E-UTRAN does not have information about the context of the UE. Accordingly, the UE in the ECM-IDLE state performs procedures related to UE-based mobility, such as cell selection or cell reselection, without a need to receive a command from a network. In contrast, when the UE is in the ECM-CONNECTED state, the mobility of the UE is managed in response to a command from a network. If the location of the UE in the ECM-IDLE state is different from a location known to the network, the UE informs the network of its corresponding location through a tracking area update procedure.

Hereinafter, a D2D operation will be described. In 3GPP LTE-A, a service related to the D2D operation is referred to as a proximity-based service (ProSe). Hereinafter, a ProSe is conceptually equivalent to a D2D operation and may be interchangeable with a D2D operation. Sidelink communication may be referred to as different terms, such as D2D communication, ProSe direct communication, and ProSe communication. Sidelink discovery may be referred to as different terms, such as D2D discovery, ProSe direct discovery, and ProSe discovery. Hereinafter, ProSe is described. A D2D operation is performed between UEs, in which an interface between the UEs may be referred to as a sidelink. A sidelink is a UE-to-UE interface for sidelink communication and sidelink discovery and corresponds to a PC5 interface.

ProSe direct discovery is a process for discovering another ProSe-enabled UE adjacent to ProSe-enabled UE. In this case, only the capabilities of the two types of ProSe-enabled UE are used. EPC-level ProSe discovery means a process for determining, by an EPC, whether the two types of ProSe-enabled UE are in proximity and notifying the two types of ProSe-enabled UE of the proximity

Hereinafter, for convenience, the ProSe direct communication may be referred to as D2D communication, and the ProSe direct discovery may be referred to as D2D discovery.

FIG. 4 shows a basic structure for ProSe.

Referring to FIG. 4, the basic structure for ProSe includes an E-UTRAN, an EPC, a plurality of types of UE including a ProSe application program, a ProSe application server (a ProSe APP server), and a ProSe function.

The EPC represents an E-UTRAN core network configuration. The EPC may include an MME, an S-GW, a P-GW, a policy and charging rules function (PCRF), a home subscriber server (HSS) and so on.

The ProSe APP server is a user of a ProSe capability for producing an application function. The ProSe APP server may communicate with an application program within UE. The application program within UE may use a ProSe capability for producing an application function.

The ProSe function may include at least one of the followings, but is not necessarily limited thereto.

Interworking via a reference point toward the 3rd party applications

Authorization and configuration of UE for discovery and direct communication

Enable the functionality of EPC level ProSe discovery

ProSe related new subscriber data and handling of data storage, and also handling of the ProSe identities

Security related functionality

Provide control towards the EPC for policy related functionality

Provide functionality for charging (via or outside of the EPC, e.g., offline charging)

A reference point and a reference interface in the basic structure for ProSe are described below.

PC1: a reference point between the ProSe application program within the UE and the ProSe application program within the ProSe APP server. This is used to define signaling requirements in an application dimension.

PC2: a reference point between the ProSe APP server and the ProSe function. This is used to define an interaction between the ProSe APP server and the ProSe function. The update of application data in the ProSe database of the ProSe function may be an example of the interaction.

PC3: a reference point between the UE and the ProSe function. This is used to define an interaction between the UE and the ProSe function. A configuration for ProSe discovery and communication may be an example of the interaction.

PC4: a reference point between the EPC and the ProSe function. This is used to define an interaction between the EPC and the ProSe function. The interaction may illustrate the time when a path for 1:1 communication between types of UE is set up or the time when ProSe service for real-time session management or mobility management is authenticated.

PC5: a reference point used for using control/user plane for discovery and communication, relay, and 1:1 communication between types of UE.

PC6: a reference point for using a function, such as ProSe discovery, between users belonging to different PLMNs.

SGi: this may be used to exchange application data and types of application dimension control information.

The D2D operation may be supported both when UE is serviced within the coverage of a network (cell) or when it is out of coverage of the network.

FIG. 5 shows the deployment examples of types of UE performing ProSe direct communication and cell coverage.

Referring to FIG. 5(a), types of UE A and B may be placed outside cell coverage. Referring to FIG. 5(b), UE A may be placed within cell coverage, and UE B may be placed outside cell coverage. Referring to FIG. 5(c), types of UE A and B may be placed within single cell coverage. Referring to FIG. 5(d), UE A may be placed within coverage of a first cell, and UE B may be placed within coverage of a second cell.

ProSe direct communication may be performed between types of UE placed at various positions as in FIG. 5.

<Radio Resource Allocation for D2D Communication (ProSe Direct Communication)>.

At least one of the following two modes may be used for resource allocation for D2D communication.

1. Mode 1

Mode 1 is mode in which resources for ProSe direct communication are scheduled by an eNB. UE needs to be in the RRC CONNECTED state in order to send data in accordance with mode 1. The UE requests a transmission resource from an eNB. The eNB performs scheduling assignment and schedules resources for sending data. The UE may send a scheduling request to the eNB and send a ProSe Buffer Status Report (BSR). The eNB has data to be subjected to ProSe direct communication by the UE based on the ProSe BSR and determines that a resource for transmission is required.

2. Mode 2

Mode 2 is mode in which UE directly selects a resource. UE directly selects a resource for ProSe direct communication in a resource pool. The resource pool may be configured by a network or may have been previously determined.

Meanwhile, if UE has a serving cell, that is, if the UE is in the RRC_CONNECTED state with an eNB or is placed in a specific cell in the RRC_IDLE state, the UE is considered to be placed within coverage of the eNB.

If UE is placed outside coverage, only mode 2 may be applied. If the UE is placed within the coverage, the UE may use mode 1 or mode 2 depending on the configuration of an eNB.

If another exception condition is not present, only when an eNB performs a configuration, UE may change mode from mode 1 to mode 2 or from mode 2 to mode 1.

<D2D Discovery (ProSe Direct Discovery)>

D2D discovery refers to the procedure used in a ProSe capable terminal discovering other ProSe capable terminals in close proximity thereto and may be referred to as ProSe direct discovery. The information used for ProSe direct discovery is hereinafter referred to as discovery information.

A PC 5 interface may be used for D2D discovery. The PC 5 interface includes an MAC layer, a PHY layer, and a ProSe Protocol layer, that is, a higher layer. The higher layer (the ProSe Protocol) handles the permission of the announcement and monitoring of discovery information. The contents of the discovery information are transparent to an access stratum (AS). The ProSe Protocol transfers only valid discovery information to the AS for announcement. The MAC layer receives discovery information from the higher layer (the ProSe Protocol). An IP layer is not used to send discovery information. The MAC layer determines a resource used to announce discovery information received from the higher layer. The MAC layer produces an MAC protocol data unit (PDU) for carrying discovery information and sends the MAC PDU to the physical layer. An MAC header is not added.

In order to announce discovery information, there are two types of resource assignment.

1. Type 1

The type 1 is a method for assigning a resource for announcing discovery information in a UE-not-specific manner An eNB provides a resource pool configuration for discovery information announcement to types of UE. The configuration may be broadcasted through the SIB. The configuration may be provided through a UE-specific RRC message. Or the configuration may be broadcasted through other than the RRC message in other layer or may be provided by UE-specific signaling.

UE autonomously selects a resource from an indicated resource pool and announces discovery information using the selected resource. The UE may announce the discovery information through a randomly selected resource during each discovery period.

2. Type 2

The type 2 is a method for assigning a resource for announcing discovery information in a UE-specific manner UE in the RRC_CONNECTED state may request a resource for discovery signal announcement from an eNB through an RRC signal. The eNB may announce a resource for discovery signal announcement through an RRC signal. A resource for discovery signal monitoring may be assigned within a resource pool configured for types of UE.

An eNB 1) may announce a type 1 resource pool for discovery signal announcement to UE in the RRC_IDLE state through the SIB. Types of UE whose ProSe direct discovery has been permitted use the type 1 resource pool for discovery information announcement in the RRC_IDLE state. Alternatively, the eNB 2) announces that the eNB supports ProSe direct discovery through the SIB, but may not provide a resource for discovery information announcement. In this case, UE needs to enter the RRC_CONNECTED state for discovery information announcement.

An eNB may configure that UE has to use a type 1 resource pool for discovery information announcement or has to use a type 2 resource through an RRC signal in relation to UE in the RRC_CONNECTED state.

Hereinafter, the present invention will be described.

The present invention proposes a method and a device for transmitting downlink control information (DCI) in a wireless communication system.

Hereinafter, a UE refers to a terminal of a user. However, when network equipment, such as a BS, transmits or receives a signal according to the communication mode between UEs, the network equipment may also be regarded as a UE.

For the convenience of description, abbreviations used in the present invention are described.

A PSBCH represents a physical sidelink broadcast channel. A PSCCH represents a physical sidelink control channel A PSDCH represents a physical sidelink discovery channel. A PSSCH represents a physical sidelink shared channel. An SLSS represents a sidelink synchronization signal. An SLSS includes a primary sidelink synchronization signal (PSSS) and a secondary sidelink synchronization signal (SSSS).

As described above, a sidelink refers to a UE-to-UE interface for D2D communication and D2D discovery. A sidelink corresponds to a PC5 interface. D2D communication may be referred to as sidelink communication or simply as communication, and D2D discovery may be referred to as sidelink discovery or simply as discovery. A D2D UE refers to a UE that performs a D2D operation, and a D2D operation includes at least one of D2D communication and D2D discovery.

Hereinafter, for the convenience of description, the present invention will be described based on 3GPP LTE/LTE-A systems. However, the present invention may also be applicable to systems other than the 3GPP LTE/LTE-A systems.

The present invention may also be applied to vehicle-to-everything (V2X) communication. V2X communication refers to a communication mode of exchanging or sharing information, such as traffic conditions, through communication with road infrastructure and other vehicles while driving. V2X may include vehicle-to-vehicle (V2V), which refers to communication between vehicles, vehicle-to-pedestrian (V2P), which refers to communication between UEs carried by a vehicle and an individual person, and vehicle-to-infrastructure/network (V2I/N), which refers to communication between a vehicle and a roadside unit (RSU) and a network. Hereinafter, V2V is illustrated as an example of V2X communication, but the present invention is not limited thereto.

UE operations related to V2V communication will be described. V2V communication refers to communication between a UE installed in a first vehicle and a UE installed in a second vehicle.

FIG. 6 illustrates scenarios in which V2V communication is performed.

Referring to FIG. 6, V2V communication may be performed in: 1) scenario 1 where only a V2V operation based on PC5, which is an interface between UEs, is supported; 2) scenario 2 where only a V2V operation based on Uu, which is an interface between a BS (eNodeB) and a UE, is supported; and 3) scenario 3 where a V2V operation is supported using both PC5 and Uu.

FIG. 7 illustrates a signaling process for V2V communication between UEs and a BS.

Referring to FIG. 7, a BS transmits a DCI format to UE #1 (S70). The DCI format may be a DCI format for mode 1, that is, a mode in which the BS schedules a resource for V2V communication. UE #1 may perform sidelink communication, for example, V2V communication, with UE #2 using the resource scheduled according to the DCI format (S71).

FIG. 8 illustrates a signaling process for V2V communication between UEs.

Referring to FIG. 8, UE #1 transmits a sidelink control information (SCI) format for V2V communication (S80). Subsequently, UE #1 may perform V2V communication with UE #2 on the basis of the SCI format (S81).

Regarding V2V communication, when a scheduling assignment (SA) and data associated with the SA are transmitted in the same subframe, a resource indicated by decoding the SA or reserved or a resource having a PSSCH RSRP of a threshold value or greater among resources for the associated data may be excluded.

Here, PSSCH RSRP in the resources for the associated data may be defined as the linear average of power distribution of resource elements carrying a DM RS associated with an associated PSSCH in PRBs indicated by the PSCCH.

A reference point for PSSCH RSRP may be an antenna connector of a UE.

For SA decoding, a UE may perform the following operations.

Resource selection/reselection may be triggered for the UE in a subframe (hereinafter, also referred to as a TTI) #n. Then, the UE may sense from subframe #n-a to subframe #n-b (a>b>0, where a and b are an integer) and may select/reselect a resource for transmission of a V2V message based on the sensing result.

Values a and b may be set commonly to UEs or may be set independently for UEs.

When a and b are common values to UEs, for example, ‘a=1000+b’. That is, when the UE is triggered to autonomously select a resource for transmission of a V2V message, the UE may perform a sensing operation for one second (1000 ms=1000 subframes=1000 TTIs).

The UE may consider SAs of other UEs in an interval from subframe #n-a to subframe #n-b. The SA may be associated with data transmission in the interval from subframe #n-a to subframe # n-b and may be transmitted before subframe #n-a.

When the UE does not perform a sensing operation in subframe #m (for example, since a signal is transmitted in subframe #m), the UE may exclude subframes #(m+100*k) from resource selection/reselection. The UE may not perform but skip a sensing operation in subframes that are used for the UE to transmit a signal.

After performing sensing, the UE selects a time/frequency resource for a PSSCH, that is, a sidelink data channel

Alternatively, upon decoding an SA in subframe (TTI) #m+c in a sensing period, a first UE may assume that the same frequency resource is also reserved in subframe #m+d+P*i by a second UE transmitting the SA. Here, P may be a fixed value of 100, and i may be selected from among [0, 1, . . . , 10] and may be carrier-specifically limited. Alternatively, i may be set to 0, which means that it is not intended to reserve a frequency resource. The value of i may be signaled via a 4-bit field in the SA.

When candidate semi-persistent resource X having a P*I period collides with resource Y reserved by an SA of another UE and satisfies a threshold condition, the UE may exclude resource X. I may be a value for i signaled via the SA.

When resources remaining after excluding resources via SA decoding and sensing are less than 20% of the total resources in a selected window, the UE may increase a threshold (e.g., 3 dB) and may then exclude a resource again, in which excluding resources may be performed until the remaining resources are greater than 20% of the total resources in the selected window.

The measurement period of the PSSCH resource may be P. The measurement may be performed only on resources remaining via the foregoing process.

In a process of selecting a V2V transmission resource after excluding a particular resource, when a counter reaches 0, the UE may maintain a current resource with a probability of p and may reset the counter. That is, a resource may be reselected with a probability of 1-p. A carrier-specific parameter p may be preset and may be set in a range of [0, 0.2, 0.4, 0.6, 0.8].

The UE measures the remaining PSSCH resources excluding the particular resource, ranks the resources on the basis of the total reception energy, and then selects a subset thereof. The subset may be a set of candidate resources having the lowest reception energy. The size of the subset may be 20% of the total resources in the selected window.

The UE may randomly select one resource from the subset.

When only one transmission block is transmitted in one subframe, the UE may select M consecutive subchannels, and the average of energy measured in each subchannel may be an energy measurement of each resource.

When a transmission block is transmitted in two subframes, the following resource selection methods may be supported. One resource may be selected using a mechanism defined for a case where a transmission block is transmitted in one subframe. Alternatively, when a particular condition is satisfied, it is possible to randomly select another resource.

The UE may not transmit a transmission block without an SA. That is, an SA also needs to be transmitted in TB transmission or retransmission.

When a resource is set such that an SA and data can be transmitted in the same subframe, the UE does not expect to combine the resource with a PSCCH transmitted in another subframe.

When a resource is set such that an SA and data are always transmitted via contiguous resource blocks in the same subframe, a subchannel having the lowest index among subchannels selected for data transmission is used for SA transmission. A resource pool may include one subchannel or a plurality of subchannels in the frequency domain. A subchannel may include consecutive resource blocks in the same subframe. The size of a subchannel, that is, the number of resource blocks included the subchannel, may be one of {5, 6, 10, 15, 20, 25, 50, 75, 100} and may be predetermined or may be set by a BS. Each subchannel may include one SA candidate resource. The SA candidate resource may also be used for data transmission.

When a resource is set such that an SA and data are transmitted via noncontiguous resource blocks in the same subframe, the number of subchannels in an associated data resource pool and the number of SA candidate resources in an SA resource pool may be the same. The SA candidate resources in the SA resource pool and the subchannels in the data resource pool may be associated 1:1. A PSSCH resource pool may include one subchannel or a plurality of subchannels in the frequency domain. A subchannel may include consecutive resource blocks in the same subframe and may be predetermined or may be set by the BS. The maximum number of subchannels in one subframe may be 20. The minimum size (the number of resource blocks) of a subchannel may be four. The PSCCH resource pool may include consecutive PRBs.

The energy sensing granularity of a PSSCH may be the size of a subchannel.

The UE may always select an integer number of contiguous subchannels for transmission.

The UE does not attempt to decode more than 100 resource blocks in one subframe and does not attempt to decode more than 10 PSCCHs.

The SA resource pool and the data resource pool may overlap.

The resource pool for V2V may be defined by a bitmap mapped to subframes other than a subframe for transmitting an SLSS. The length of the bitmap may be any one of 15, 20, and 100. The bitmap may indicate/define a subframe in which SA/data transmission/reception for V2V is allowed.

When resource reselection is triggered, the UE reselects resources for all transmissions corresponding to a transmission block. An SA schedules only transmission corresponding to one transmission block.

Hereinafter, (A) an SCI format configuration field(s) used in a mode-2 V2V scheduling (MODE2_SCH) operation and/or (B) a DCI format configuration field(s) used in a mode-1 dynamic V2V scheduling (MODE1_DYN) will be described. Here, mode 1 is a mode in which a BS schedules a resource for V2V communication, and mode 2 is a mode in which a UE selects a resource for V2V communication from a resource pool set by a network or predetermined.

SCI may be control information transmitted by a UE in a sidelink, may be 48 bits in total, and may include the following fields.

Priority: 3 bits, resource reservation: 4 bits, MCS: 5 bits, CRC: 16 bits, retransmission index: 1 bit, time gap between initial transmission and retransmission: 4 bits (Here, this field has one value of 0 to 15, in which 0 denotes no retransmission of a related transmission block), frequency resource location (FRA_INRETX) for initial transmission and retransmission: 8 bits, reserved bits: 7 bits. RV 0 and 2 are sequentially used for initial transmission and retransmission.

DCI transmitted by a BS for dynamic scheduling for a sidelink may include the following fields.

CIF: 3 bits (an interpretation of the CIF may be preset and may be different from that of a CIF for uplink and downlink), lowest (smallest) index of subchannel assigned for initial transmission (PSCCH_RA): 5 bits, SA content: i) time gap between initial transmission and retransmission (TGAP_INRETX: 4 bits), ii) frequency resource location for initial transmission and retransmission (FRA_INRETX: 8 bits). The length of the DCI may be the same as DCI format 0, and an RNTI other than a C-RNTI/SPS-RNTI may be used. A time location for initial transmission may be the first subframe included in a resource pool of a V2V carrier and may be a subframe 4 ms after a subframe in which the DCI is transmitted.

It is assumed that the maximum number of subchannels (referred to as SF_MAXNUMSCH), which can be included in a V2V resource pool, in one subframe is (always) 20, the payload size of a MODE1_DYN DCI format may be a total of 20 bits (e.g. “3 (=CIF)+5 (=PSCCH_RA)+4 (=TGAP_INRETX)+8 (=FRA_INRETX)=20”).

When the payload size of the MODI1_DYN DCI format is matched to that of existing DCI format 0, the payload size of the MODI1_DYN DCI format (e.g., 20 bits) may become greater than that of DCI format 0 (e.g., 19 bits (1.4 MHz)) at a particular system bandwidth (e.g., 1.4 MHz). To solve this problem, (some) methods are proposed as follows.

For example, a V2V (PSSCH (/PSCCH)) resource pool may be configured by (information) signaling (A) the total number of subchannels included in the V2V resource pool in one subframe, and/or (B) the number of resource blocks included in a (single) subchannel (subchannel size), and/or (C) the starting location of a subchannel (RB) in the frequency domain, and/or (D) the location of a subframe where the V2V resource pool is set (e.g., a predefined length (e.g., a bitmap format of 16, 20, or 100)) (and/or (E) the starting location of a subchannel (RB) (in the frequency domain) of a (E)PSCCH resource pool (this information may be valid (present) only when a PSCCH and a (linked) PSSCH are not located on contiguous resource blocks in the same subframe)).

The following (some) proposed methods may be extended to (determination of FRA_INRETX size in) an SCI format associated with the MODE2_SCH operation.

The following table illustrates the payload size of existing DCI format 0 in each system bandwidth.

TABLE 1 DCI format 0 Bandwidth 1.4 3 5 10 15 20 MHz MHz MHz MHz MHz MHz Hopping flag 1 1 1 1 1 1 N_ULHOP 1 1 1 2 2 2 Resource block assignment 5 7 7 11 12 13 MCS & RV 5 5 5 5 5 5 NDI 1 1 1 1 1 1 TPC for PUSCH 2 2 2 2 2 2 Cyclic shift for DMRS 3 3 3 3 3 3 CQI request 1 1 1 1 1 1 Total bits 19 21 21 26 27 28

[Proposed method #1] For example, the size of FRA_INRETX (and/or PSCCH_RA) included in DCI format 5A can be changed depending on the total number of subchannels (TSUBNUM_SF) included in a V2V resource pool (in one subframe) set (signaled) in advance. Here, DCI format 5A is a DCI format used for PSCCH scheduling and may also include fields used for PSSCH scheduling.

FIG. 9 illustrates a method for determining the payload size of DCI format 5A according to proposed method #1.

Referring to FIG. 9, a BS may determine the number of subchannels (=TSUBNUM_SF) of a V2V resource pool in a subframe (S100) and may change the payload size (frequency resource location field for initial transmission and retransmission) of DCI format 5A according to the number of subchannels (TSUBNUM_SF) (S110). Here, a subchannel may include a plurality of contiguous resource blocks in the same subframe. For example, the BS may adjust the number of resource blocks included in a subchannel, thereby adjusting the size of a resource allocation (RA) field of DCI format 5A. Accordingly, it is possible to prevent the total payload size of DCI format 5A from being greater than that of DCI format 0.

For example, when the total number of subchannels (TSUBNUM_SF) included in a V2V resource pool within one subframe is K, the size of FRA_INRETX (frequency resource location field for initial transmission and retransmission) (and/or PSCCH_RA (lowest (smallest) index field of a subchannel assigned for initial transmission)) included in DCI format 5A may be CEILING(LOG₂(K·(K+1)/2)) (and/or “CEILING (LOG₂(K))”). Here, CEILING(X) is a function for deriving a minimum integer value that is equal to or greater than X.

For example, when the total number of subchannels (TSUBNUM_SF) included in a V2V resource pool within one subframe is 10, the size of FRA_INRETX (and/or PSCCH_RA) may be six bits (and/or four bits).

When this rule is applied, TSUBNUM_SF (number of subchannels) is properly set (signaled) (by a network), thereby solving the foregoing problem such that the payload size (e.g., 20 bits) of the MODE1_DYN DCI format is greater than the payload size (e.g. 19 bits) of existing DCI format 0 in a 1.4 MHz system bandwidth.

For example, the size of FRA_INRETX (and/or PSCCH_RA) can be changed according to the FLOOR value (the number of resource blocks included in a system bandwidth/(one) subchannel (subchannel size)) (which is referred to as MAX_SUBVAL). Here, FLOOR(X) is a function for deriving a maximum integer value that is less than or equal to X.

For example, when MAX_SUBVAL=K, the size of FRA_INRETX (and/or PSCCH_RA) may be changed to CEILING(LOG₂(K·(K+1)/2)) (and/or CEILING (LOG₂(K))).

[Proposed method #2] For example, (when proposed method #1 is applied) remaining bits of “(payload size of (existing) DCI format 0−CEILING(LOG₂(K(K+1)/2)) (=FRA_INRETX size)−3(=CIF)−5(=PSCCH_RA)−4(=TGAP_INRETX))” (and/or remaining bits of “(payload size of (existing) DCI format 0−CEILING(LOG₂(K(K+1)/2)) (=FRA_INRETX size)−3(=CIF)−CEILING(LOG₂(K))(=PSCCH_RA size)−4(=TGAP_INRETX)” can be set to a value (e.g., 0 or 1) designated by a (serving) BS (or network) through predefined (higher/physical)-layer (e.g., SIB or RRC) signaling or may be (always) padded with zeros (by a UE). The remaining bits may be used as a virtual CRC.

The application of (some of) this rule may be interpreted such that additional extra bits, which occur when the FRA_INRETX size is changed according to proposed method #1 (in MODE1_DYN DCI format and/or MODE2_SCH SCI format), (e.g., “(8−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETX size))” (and/or “(8−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETX size)−CEILING(LOG₂(K))(=PSCCH_RA size))”)) (and/or the (target) payload size predefined (signaled) (e.g., (additional) extra bits, which occur when the FRA_INRETX size is changed according to proposed method #1, the (target) payload size in MODE1_DYN DCI format and the (target) payload size in MODE2_SCH SCI format may be the payload size of (existing) DCI format 0, which is 48 bits) may be set to a value designated by a (serving) BS (or network) through predefined (higher/physical)-layer signaling or may be (always) padded with zeros (by a UE).

FIG. 10 illustrates a case where proposed method #2 is applied.

Referring to FIG. 10, an SCI format (e.g., SCI format 1) according to the present invention may include a priority field (=3 bits), a resource reservation field (=4 bits), an RA field (which indicates a frequency resource location for initial transmission and retransmission, may be a resource allocation field, and may be 8 bits), a field for a time gap between initial transmission and retransmission (=4 bits), an MCS field (=5 bits), a retransmission index field (=1 bit), a reserved information field (=7 bits), and a CRC field (=16 bits). That is, SCI format 1 has a total of 48 bits, and information bits excluding CRC bits are 32 bits. For SCI format 1, the total number of bits, that is, the total size, is fixed, and the size of the RA field may also be fixed to 8 bits. However, even though the size of the RA field is fixed, the number of actually used bits is not always eight. That is, only fewer than eight bits may be used depending on the number of subchannels. In this case, according to the present invention, bits other than used bits in the RA field are padded with zeros. The bits other than the actually used bits in the RA field may be padded with zeros and may then be used as a virtual CRC.

For the sake of understanding, the present invention is compared with the prior art. First, in DCI format 0, the size of the RA field is not fixed but is variable. That is, the number of bits for the RA field changes depending on the number of resource blocks (allocated) to the entire system. Thus, the total length (size) of DCI format 0 is also not fixed but is variable. Even though DCI format 1A is padded with zeros corresponding to the total length of DCI format 0, such zero padding is not padding a particular field having a fixed length with zeros as in the present invention but is padding DCI format 1A with zeros corresponding to the variable total length of DCI format 0. Thus, such zero padding is completely different in mechanism from the present invention.

FIG. 11 illustrates a method in which proposed method #2 is applied.

Referring to FIG. 11, a UE determines the number of bits to be actually used in a resource allocation field of SCI format 1 (S500) and pads, with zeros, bits other than the bits to be actually used in the resource allocation field (S510).

That is, in generating an SCI format and transmitting the generated SCI format to another UE, the UE may determine the number of bits to be actually used in a resource allocation field included in the SCI format and may pad, with zeros, bits other than the bits to be actually used in the resource allocation field, thereby transmitting the SCI format. The number of bits to be actually used in the resource allocation field may be determined depending on the number of subchannels allocated to the UE.

When proposed method #1 is applied, if an (mode-1) SPS operation-related field (e.g., SPS configuration (/activation(/release)) indicator) (SPS_PALD) needs to be further defined in a MODE1_DYN operation-related DCI format, a TSUBNUM_SF value may be (limitedly) set (/signaled) when a condition is satisfied that remaining bits of “(payload size of (existing) DCI format 0−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETX size)−3 (=CIF)−5(=PSCCH_RA)−4 (=TGAP_INRETX)−SPS_PALD size)” (and/or remaining bits of “(payload size of (existing) DCI format 0−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETX size)−3(=CIF)−CEILING(LOG₂(K)) (=PSCCH_RA size)−4 (=TGAP_INRETX)−SPS_PALD size)” is greater than 0.

The illustrative proposed methods described above may also be included as methods for implementing the present invention and thus may be regarded as a kind of proposed schemes. In addition, the proposed methods described above may be implemented independently, but some of the proposed methods may be combined (or merged) for implementation.

Although the present invention has been described with reference to the proposed methods based on 3GPP LTE/LTE-A systems for the convenience of description, the scope of systems to which the proposed methods are applied may be extended to other systems besides the 3GPP LTE/LTE-A systems.

The proposed methods of the present invention may also be extended for D2D communication. Here, D2D communication refers to communication between one UE and another UE via a direct wireless channel A UE may be a terminal of a user. Further, when network equipment, such as a BS, transmits or receives a signal according to the communication mode between UEs, the network equipment may also be regarded as a UE.

The proposed methods of the present invention may be applied only to a mode-2 V2X operation (and/or mode-1 (sidelink dynamic scheduling and/or sidelink SPS and/or uplink SPS) V2X operation).

The proposed methods of the present invention may be limitedly applied only when a PSCCH and a (linked) PSSCH are not located (or are located) in contiguous resource blocks in the same subframe.

In addition, the proposed methods of the present invention may also be applied not only to a V2V mode-1 (/mode-2) dynamic scheduling operation but also to a V2V mode-1 (/mode-2) semi-static scheduling (SPS) operation (and/or a V2X mode-1 (/mode-2) dynamic scheduling operation and/or a V2X mode-1 (/mode-2) SPS operation).

In the present invention, the term “mode 1” (or “mode 2”) may be interpreted as (/replaced with) “mode 3” (or “mode 4”) related to V2X communication.

(All or some of) The proposed methods of the present invention may be applied to DCI and/or SCI associated with V2X communication.

FIG. 12 is a block diagram illustrating a device to implement an embodiment of the present invention.

Referring to FIG. 12, the device 1100 includes a processor 1110, a memory 1120, and a radio frequency (RF) unit 1130. The device 1100 may be a base station, a relay station, or a UE. The processor 1110 performs a proposed function, process and/or method.

The RF unit 1130 is connected to the processor 1110 and transmits and receives radio signals. The memory 1120 may store information necessary for driving the processor 1110 and/or the RF unit 1130.

The processor may comprise an application-specific integrated circuit (ASIC), other chipset, logic circuitry and/or data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and/or other storage devices. The RF unit may include a baseband circuit for processing the radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module may be stored in the memory and may be executed by the processor. The memory may be internal or external to the processor, and may be coupled to the processor by various well known means. 

What is claimed is:
 1. A method for transmitting, by a user equipment (UE), sidelink control information (SCI) in a wireless communication system, the method comprising: generating an SCI format; and transmitting the generated SCI format to another UE, wherein the SCI format is transmitted by determining a number of bits to be actually used in a resource allocation field of the SCI format and padding, with zeros, bits other than the bits to be actually used in the resource allocation field.
 2. The method of claim 1, wherein a total number of bits comprised in the SCI format is a fixed value.
 3. The method of claim 2, wherein the total number of bits is 48 bits.
 4. The method of claim 1, wherein a number of bits comprised in the resource allocation field of the SCI format is a fixed value.
 5. The method of claim 4, wherein the number of bits comprised in the resource allocation field is 8 bits.
 6. The method of claim 1, wherein the number of bits to be actually used in the resource allocation field of the SCI format is determined depending on a number of subchannels allocated for the UE.
 7. The method of claim 6, wherein the subchannels comprise a plurality of contiguous resource blocks.
 8. A device for transmitting sidelink control information (SCI) in a wireless communication system, the device comprising: a radio frequency (RF) unit to transmit and receive a radio signal; and a processor connected to the RF unit to operate, wherein the processor generates an SCI format and transmits the generated SCI format to another UE, and the SCI format is transmitted by determining a number of bits to be actually used in a resource allocation field of the SCI format and padding, with zeros, bits other than the bits to be actually used in the resource allocation field.
 9. The device of claim 8, wherein a total number of bits comprised in the SCI format is a fixed value.
 10. The device of claim 9, wherein the total number of bits is 48 bits.
 11. The device of claim 8, wherein a number of bits comprised in the resource allocation field of the SCI format is a fixed value.
 12. The device of claim 11, wherein the number of bits comprised in the resource allocation field is 8 bits.
 13. The device of claim 8, wherein the number of bits to be actually used in the resource allocation field of the SCI format is determined depending on a number of subchannels allocated for the UE.
 14. The device of claim 13, wherein the subchannels comprise a plurality of contiguous resource blocks. 